As new COVID-19 cases spike in the U.S., and ahead of an expected winter surge, the FDA just issued its first full approval for a drug to treat the disease—Gilead Sciences’ Veklury, formerly known as remdesivir. But the approval closely follows a large trial that showed no benefit for the therapy, and experts quickly questioned the FDA’s move.

Veklury won approval to treat COVID-19 requiring hospitalization in adults and children 12 and older. Simultaneously, the FDA issued a new emergency use authorization for certain patients under 12. The agency approved the med based on late-stage trials showing Veklury is associated with an improved time to recovery and reduced disease progression in hospitalized patients, Gilead said.

Just last week, though, a large trial from the World Health Organization (WHO) cast doubts on the med’s efficacy. WHO released preliminary results from a trial of 11,266 COVID-19 patients in 30 countries on one of four drug regimens, including Veklury. The medicine “appeared to have little or no effect on hospitalized COVID-19,” the researchers wrote in a study posted (PDF) on the journal preprint site medRxiv.

Gilead responded that it was “concerned that the data from this open-label global trial have not undergone the rigorous review required to allow for constructive scientific discussion, particularly given the limitations of the trial design.”

Weighing in on the approval, two prominent doctors said the data don’t yet support the FDA’s decision. The green light was “astonishing,” Peter Bach, director of Memorial Sloan Kettering’s Center for Health Policy and Outcomes, wrote on Twitter.

“Of the three included studies, one lacked control, two lacked blinding, all three lacked inclusion of current standard of care,” he wrote. The results were mixed, he pointed out, and a randomized study larger than the three touted by the FDA combined was “entirely negative.”

For his part, Eric Topol, M.D., director of the Scripps Research Translational Institute, wondered how the drug could get a full approval based on the “mixed data.” It’s unclear whether the med works early or late, and there’s still much “unresolved,” Topol wrote.

WHO designed its trial to rapidly evaluate treatments in large patient groups. Gilead argued the broad patient group makes it “unclear if any conclusive findings can be drawn from the study results.”

Before that, a study led by the U.S. government showed the med, tested against placebo, improved recovery times, reduced chances of patients progressing to more severe stages of illness and significantly cut the risk of death in patients on low-flow oxygen. Patients on the drug recovered five days faster than those on placebo on average, and severe patients recovered seven days faster.

For patients on low-flow oxygen, investigators recorded 70% fewer deaths in the remdesivir group than in the placebo group.

Despite questions about the data, the drug has become a standard treatment, as evidenced by its use in President Donald Trump earlier this month. The FDA authorized it for emergency use in May, and Gilead has spent much of 2020 working to scale up capacity.

Gilead expects big revenues from the medicine in 2020, and, earlier this year, the drugmaker raised its revenue guidance by billions of dollars due to blockbuster Veklury expectations.